Cyanide in the Real World

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Nurses Edition Commentary

Mizuho Morrison, DO, Lisa Chavez, RN, and Kathy Garvin, RN

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Brooks W. -

The comment about the “50% ROSC rate” could be discussed a bit further.

The 50% figure comes from Fortin 2006, where 21 out of 38 fire victims in cardiac arrest were given hydroxocobalamin (HCB) at some point during EMS management. Unfortunately, all but 2 of those patients later died in the ICU. Also, it is important to highlight that the authors did not specify if those 21 ROSC patients received the HCB before, during, or after ROSC.

“But,” you might think, “of _course_ they got the HCB before ROSC!” The same lead author, however, later published a similar case series (Fortin 2010), where 5/61 fire victims in cardiac arrest survived to hospital discharge. They explained that 4 of these patients had ROSC *before* the HCB was pushed. In the authors’ words:

“Among the 61 patients in [cardiac] arrest, 5 survived without sequelae and, in particular, without neurological sequelae. Four of the 5 patients were ... discovered in cardiac arrest by the fire brigade, and spontaneous cardiac activity was obtained after cardiac massage and oxygen therapy. ... [H]ydroxocobalamin was not responsible for the recovery of spontaneous cardiac activity in these patients."

Anyway, there are 2 other small case series in the literature, but it isn’t worth reviewing them here. These were simple case series, without any controls, or even a “before & after” design, so we have no idea if this cyanide antidote actually saves lives in cardiac arrest in fire victims. Heck, it might even decrease save rates – we couldn’t possibly know, though, because of the design of the studies.

I agree that the mechanism is elegant, the drug is likely darn safe, and that some (not all!) of the animal models look compelling. But the human data is messy, at best, and no conclusions about “save rates” could possibly be drawn from it. Since we can’t even show that epinephrine helps in cardiac arrest, I’m not holding my breath about HCB!

Jennifer C., MD -

I'm late to this party since I am a few months behind on EMRAP. I'm a toxicologist as well as an ER Doc, and if someone runs out of a building and collapses from CN poisoning, the changes of them being able to receive any antidote fast enough to save them is low. It would definitely need to be in the field, as they will likely be dead before hospital arrival if they collapsed on scene from CN. And in the field, you do not know if they have CO poisoning, so as noted in the talk, Lilly kit could be dangerous. However, hydroxocobalamin is not the fastest acting drug, and is administered over 15 min, and can interfere with later pulse oximetry and also carboxyhemoglobin measurements. In conjunction with statement above on limited efficacy data, I agree that it may not be the best idea to give somewhat indiscriminately to unconscious fire victims in the field.

Howard M. -

Hi Jen,

It is never a problem to be late on EM:RAP, the party is always hopping. While I respect your trepidation, what is it you would like EMS to do with the unconscious fire patient? We have good data that demonstrate that cyanide and carbon monoxide are frequent co-exposures, especially in fire fatalities ( As pointed out, if we wait until hospital arrival it will be too late. The Lilly kit has too many side effects for empiric use. But what is the downside (other than cost) to high flow O2 and hydroxocobalamin together to treat the two most likely problems? This has been the successful approach of the FDNY, Paris fire brigade, and many other large fire departments. Anecdotally, the FDNY reports great outcomes. Physiologically, I do not see the downside. Is there a different approach we should be using?

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